The invention relates to an aqueous release agent, which as release-active substances contains oil and/or wax emulsified in water as the carrier, as well as the use thereof.
Polyurethane foam articles are produced in moulds and this can take place according to the most varied prior art processes. A large number of variants, which are known to those skilled in the art, are possible with respect to the foam-forming components used and with respect to the equipment and moulds used. Generally the mould is filled in the open or closed state through a feed channel with the polyol and isocyanate components mixed by means of a mixing head. Apart from the sought product and its desired characteristics, the composition of the components is also decided by whether working is to take place according to the single-stage process (direct process) or the two-stage process (prepolymer or semi-prepolymer process). All these different possible procedures are described in detail in the literature, so that there is no need to comment further thereon. Reference is e.g. made to "Integralschaumstoffe", Piechota and Rohr, 1975; Kunststoff-Handbuch, vol. VII, "Polyurethane", 1966; "Schaumkunststoffe", published by the Fachverband Schaumkunststoffe in GKV, 1976; Wittfoht, "Kunststoff-Technisches Worterbuch", Part 3.
For the purpose of the easier and cleaner removal of the foam articles polymerized in the metal, wood or plastic moulds, the mould surfaces coming into contact with the foam-forming components or the polyurethane foam are treated with release agents (mould release agents) prior to filling the mould. For this purpose the mould surfaces are provided with a uniform release compound coating, to produce a release film thereon. This generally takes place by spraying or injecting, the release compound either being atomized by pressurizing the material itself or by e.g. the use of pressurized air. Apart from good mould release characteristics, in special cases the release agent must also be able to exert an influence upon the surface characteristics of the finished polyurethane foam article. Thus by the addition of certain additives, e.g. in the cold flexible foam field (seats, headrests, armrests, etc. in cars) the desired open-cell characteristics are produced along with the necessary "breathability" of the foam article.
Conventional release agents consist of organic solvents and release-active substances dissolved, dispersed, suspended or emulsified therein and which are referred to as solids. With regards to the disadvantages of such release compounds, particularly from the environmental standpoint and the long-lasting efforts to develop aqueous release agents, reference is e.g. made to European Patent Application No. 164501, European Patent Application No. 188219 and German Patent Application No. P 35 41 513. As can be gathered from the aforementioned applications, there is a considerable need for aqueous release compounds for use in processes for producing polyurethane foam articles where, apart from the desired good mould release characteristics, characteristics are also required with regards to release agent processability of the type known from conventional release agents based on organic solvents.
Objects of the present invention are therefore to provide aqueous release compounds of the aforementioned type, which have excellent mould removal characteristics, in use lead to polyurethane articles with good surface characteristics and as a function of the cycle times can be used at the temperatures required for obtaining adequately short venting times.